Remote control system



Jam 16, 1 940w P. H. CRAGO REMOTE CONTROL SYSTEM 5 Sheets-Sheet 1 Filed April 16, 1938 a m 5 Q c P 4 H w W 5 5 6W3 wa 0 M V Z. w w P K 0 c R 4 Q m w m 23 z w P 63 P M 5 m 8 P m I W 4 5 m m w M 3 a d ai 0 0 B 2 W 0;. w P 2 w P p a M 6 WM Jan. 16, 1940. P. H. cRA o I 2,137,414

' REMOTE CONTROL SYSTEM Filed April 16. 1938 5 Sheets-Sheet 3 XL TM] I I I I. I l I I I I I. l I

I I I I I I l I I I I I I l I I I I I l I I. I. I T I I INVENTOR Jan 16, 1940, P. H. CRAGO 2,17,414-

REMOTE CONTROL SYSTEM Filed April 16. 1938 5 Sheets-Sheet 4 i l N 1 i I 169' m 5,0 v 20 W Big" W44 5 fizao lf Coder 00 N p131 MEL.

l ff 154 2 1% Lm 44: P9 P 155 153 i [3 15"? r T P1154 EA w 1150 B L 1 Field $51, 46 Brawn. x149 Nefwofije. RG13 4.9 La? i a N 10 3 J g El: 1] j 95 B i C fi m fi i E; fi E T? g C LBH 7 LAN LB 1 35H 15; 139 I LP :18!) RM 3 156 1 156 1 i 21). lNVENTOR Paul Cpayo;

H15 ATTORNEY Jan. 16, 1940. P. H. CRAGO REMOTE CONTROL SYSTEM Filed April 16, 1938 5 Sheets-Sheet 5 j wmh h INVENTOR Paul H 1 HIS ATTORNEY Patented Jan. 16, 1940 UNITED srArizs REMOTE CONTROL SYSTEM Application April 16,1938, Serial No. 202,507

29 Claims.

further feature of my invention is the provision.

of novel and improved apparatus that permits, by

the use of code following contact members, the

transmitting of different control influences from an office station to a remote field station and the returning of different indication influences to the office station over a line circuit comprising a sin gle line wire and a common return wire. By the use of such code following contact members, one at each station, it is possible to apply control and indication influences alternately to the 0pposite ends of the line circuit so spaced in time relation that overlapping of the impulses is avoid ed. Still another feature of my invention is the provision of novel and improved apparatus that permits by the use of apilot line circuit the transmission of four different indications over a single two-wire line circuit, at least three of which indications are entirely'independent of each other and may be displayed in any combination. Other features and advantages of my invention will appear as the specification progresses.

I shall describe three forms ofapparatus embodying my invention, and shall then point out the novel features thereof in claims. 40 In the accompanying drawings, Figs. la and 119, when taken together with Fig. 1a placed at the left of Fig. 1b, are a diagrammatic View of one form of apparatus embodying my invention when applied to the control of a railway track switch and its related signals from an oiiice station and to the indicating at the, ofiice station of the positions of the track switch and signals, and also the occupancy of track sections in the vicinity of the track switch. Figs. 2a and 2b, 50 when taken together with Fig. 2a placed at the left of Fig. 2b, are a diagrammatic view of a sec- 0nd form of apparatus embodying my invention when applied to the control of a railway track switch and its related signals and to the indicating of the positions of the switch and Signals and the occupancy of track sections in the vicinity of the switch. Fig. 3 is a diagrammatic view of a third form of apparatus embodying my invention when applied to thecontrol of a track switch and its related signals and to indi-- cating their positions and the occupancy of the associated track sections. In each of the different views, like reference characters designate similar parts.

It will be understood that my invention is not limited to the control and indication of railway track switches, signals and occupancy of track sections. This one application of the invention will serve, however, to illustrate the many places where the invention may be used.

To simplify the drawings in order that they may be more readily understood, I have in many instances illustrated relay contact fingers remote from the relay windings which operate them. In all such instances, the reference character of the corresponding relay is placed adjacent the contact finger, and the finger is shown in the position corresponding to the normal energized or deenergized condition of the relay winding. In several instances I have also shown circuit controlling contacts remote from the devices which operate them. Such contacts are identified by placing the reference character of the associated device adjacent the contact, and by the contact being shown in the position corresponding to the normal position of the device. Furthermore, in the following description current of positive polarity will at times be referred. to as current,

of normal polarity, and current of negative polarity will at times be referred to as current of reverse polarity.

Referring to Figs. la and 1b, the reference characters Ma and ill) designate the track rails of a stretch of railway track which are formed by the usual insulated rail joints into track sections IT, ET and 3T, a track switch SW being located in track section 2T. Each of these track sections is provided with a track circuit comprising a current source, such as a battery connected across the rails at one end of the section and a track relay designated R plus a prefix corresponding to the section connected across the rails at the other end of the section.

Two signals RA and RB govern eastbound traffie, that is, traflic moving from left toright in Fig. 127, through the track section ET and over the track switch SW, the two signals being mounted on the same mast. Two signals LA and LB govern westbound traffic, that is, traffic moving from right to left in Fig. lb, through the track section 2T and over the switch SW. These signals may be of any suitable type and are shown conventionally. It will be understood, of course, that other signals governing traffic approaching the signals RA, RB, LA and LB would be provided in accordance with standard practice, but these other signals are not shown since they are not required to illustrate my invention. The track switch SW is moved to its normal and reverse positions through the medium of a power operated switch mechanism SM, which may be of any standard type.

The track switch SW and its related signals are controlled through the medium of apparatus placed partly at a field station FS located adjacent the switch SW and partly at a remote office station DS, such as a dispatcliers ofilce. The apparatuses at the two stations are interrelated by virtue of line circuits extending between the two stations, and which line circuits will be more fully described hereinafter. The two stations FS and DS are equipped with proper sources of current, such as a battery IE5 at the station FS and a battery H at the station DS. These two batteries 16 and H are each provided with a positive terminal B, a negative terminal N, and a center or common terminal C, the terminal C being connected with a common return line wire designated by the reference charac ter CL, and which line wire serves as a common side for the above-mentioned line circuits.

Referring first to the apparatus at the field station FS, the operating circuits for each signal are governed by a signal control relay designated by the reference character I-I plus a prefix corresponding to the signal. The operating circuits for each signal are those of standard practice, and are not shown for the sake of simplicity. It is deemed sufiicient for this application to point out that when a signal control relay is deenergized the associated signal is set to display a stop indication, and when the relay is energized the signal is set to display a proceed indication. For example, when the signal control relay RAH for signal RA is deenergized, the signal RA is operated to its stop position, and when the relay RAH is energized the signal RA is operated to a proceed position.

signal control relays are in turn governed by two remote control relays LGR and RGR, to be described later, as well as by traffic conditions and the position of the track switch SW. The control of the signal control relays by traffic conditions is illustrated conventionally by trafiic controlled networks 12 and '55 since such control is not involved in my present invention, and it may be that shown and described in my copending application for United States Letters Patent, Serial No. 631,041, filed August 30, 1932, for Remote control system, now Patent No. 2,124,651. The relays RAH and RBH are selectively governed over a circuit comprising the trafiic controlled circuit network it, front contact 13 oi control relay RGR, back contact M of control relay LGR and a contact SW 1 operated by the track switch SW, the relay RAH being selected when the switch SW is set at its normal position and the contact SW! occupies the full line position, and the relay RBH being selected when the switch is set at its reverse position and the contact SW! occupies the dotted line position. In a similar fashion, the signal control relays LAI-I and LBH are selectively governed over a circuit comprising the trafiic controlled circuit network '75, back contact 53 of relay RGR, front contact 17 of relay LGR and a contact SW2 operated by the track switch, the relay LAI-I being selected when the switch is normal so that the contact SW2 occupies the solid line position and the relay .LBH being selected when the switch is in its reverse position so that the contact SW2 occupics the dotted line position. Consequently, when the control relay RGR is picked up and the control relay LGR is released, in a manner to be later described, the signal control relay RAH or RBI-I is energized according to the position of the track switch, it being assumed, of course, that the traffic controlled circuit network 72 is also closed. Again, when the control relay LGR is picked up and the control relay RGR is released, the relay LAH or LEI-I is selected according to the position of the track switch, the trafiic con trolled network i5 being assumed to be closed.

Two approach locking relays RMR and LMR, a repeater relay MPv and a time element relay TE are provided in the field station apparatus of Fig. 1b forgoverning, as is the custom in systems of this character, the operation of the switch and signals. The approach locking relays RMR and LMR are normally energized over traiiic controlled networks of any standard form responsive to traific approaching the switch SW and which networks are here indicated by reference characters 3 and B. One form of traflic controlled network that may be used is that shown in my aforementioned application Serial No. 631,041. As illustrated, the relay RMR is normally energized by a circuit extending from terminal B of battery i6 over back contacts 4 and 5 of relays RBI-I and RAH, respectively, network 3, winding of relay RMR and battery terminal C. In a like manner, the relay LMR is energized over a circuit extending from battery terminal B, back contacts I and 8 of relays LBH and LAH, respecively, network 6, winding of relay LMR and terminal C. In shunt with the network 3 is a front contact 25'! of the time element relay TE, and another front contact 2H3 of relay TE is disposed in shunt with network 6. It follows that when signal control relay RAH or RBH is picked up to operate the corresponding signal the locking relay RMR is deenergized and if relay RBH or RAH is subsequently released while the network 3 is opened in response to traffic conditions, the relay RMR can be reenergized by operation of relay to close front contact 217. In like fashion, the locking relay LMR can be reenergized while the network 6 is open in response to traffic conditions by operation of relay TE to close front contact M8. The time element relay TE is of the usual type which requires its winding to be energized a selected period of time. for example, one minute, before its front contacts 2i! and 2 it are closed. The repeater relay MP is controlled by a circuit having two branch paths, one path of which includes front contact 225 of relay LMR and back contacts M8, 5 and 4 of relays RAH and RBH, respectively; and the other path involves back contacts 22%. 8 and i of relays LMR, LAI-I and LBH. respectively. The relay MP controls at its front contact Hi the operation of the time element relay TE.

The immediate control of the switch mechanism SM is accomplished by a polarized switch controlling relay WR. The operating circuits governed. by relay WR for reversibly operating the mechanism SM are not shown since these circuits are not required for an understanding of present invention. Although the operating circuits controlled by relay WR may be any one of the forms in present day use, they would be preferably those disclosed in my aforementioned application Serial No. 631,041, to which reference is made for a full understanding of such switch operating circuits. It is sufficient in the instant case to say that when relay WR is energized with current of positive or normal polarity the mechanism SM is operated to move the switch to its normal position, that is, the position illustrated in Fig. 117. When relay WR is energized with current of negative or reverse polarity, the mechanism SM is operated to move the track switch to its reverse position, that is, the position opposite that illustrated in Fig. 1b. The relay WR is normally deenergizecl, is energized only during a movement of the switch, and is provided with slow release characteristics.

The relay WR is in turn controlled by the remote control relays LGR and RGR over circuit networks preferably similar to those disclosed and described in my copending application Serial No. 631,041, and which networks are designated conventionally in Fig. 1?) by the reference characters ill and II. It should be pointed out that when both control relays LGR and RGR are picked up the relay WR is supplied with current opposite in polarity from that by which the relay was last energized. For example, with the switch SW in its normal position, the relay WR was last energized by current of normal polarity, and thus if the relays LGR and RGR are both picked up, closing their respective front contacts l3 and 42, a circuit is formed from the negative terminal N over circuit network H, front contacts i2 and. S3, winding of relay WR and terminal C, and. the relay WR is energized by current of negative or reverse polarity. In response to an operation of the switch to the reverse position, the network is prepared and the network I l is opened, the relays LGR and RGR being re leased before network ill is closed. The next operation of relays RGB and LGR to close their respective front contacts I2 and I3 completes a circuit from the positive terminal B of the current source over network. Iii, front contacts i2 and i3, winding of relay WR and terminal C, and the relay i/VR is supplied with current of positive or normal polarity.

A switch indication relay KR. is controlled over a pole changer M which is operatively connected with the mechanism SM and the switch SW, as indicated by a dash line E5, the arrangement besuch that relay KR is energized by current of normal polarity when the switch is in its normal position and is energized by current of reverse polarity when the switch is moved to its reverse position. The relay KR is also preferably governed by the control relays RGR and Lil-Pt in the manner described in my aforementioned application Serial No. 631,041, and which control is here indicated by contact me, the arrangement being such that when relays RGB and LGR are both. picked up the contact Hi9 is open and relay KR is released.

Before describing the apparatus at the oilice station Did, I shall point out the pilot line circuit extending between the two stations, and which pilot line circuit forms an essential element of my present invention. In Figs. 1a. and 1b this pilot line circuit seriallyincludes the windings of two code following relays ICF and ZCF, the relay ICF being located at the oifice station and the relay being located at the field station. This pilot line circuit can be traced from the B terminal of the battery 11 at the office station over code contact member l8 and contact IQ of a code transmitter DC, winding 20 of relay ICF, line wire PL to station FS, winding 2d of relay ZCF, and the common return wire CL back to the terminal C of battery ii. The type of code transmitter DC is immaterial and, as here shown, its contact member i8 is operated between the full line position and the dotted line position at a predetermined rate of, say, for example, 120 times per minute when the winding 22 of the code transmitter is energized. In Fig. 1a,, the winding 22 of the code transmitter DC is connected across the terminals B and C of the current source and is continually active, so that the pilot line circuit is periodically opened and closed at the pre-. determined rate here assumed as 120 times per minute. It follows that the two code following relays ICE and ZCF are operated in synchronism so that when the pilot circuit is closed the contact members 23, 24 and 25 of relay ICF and the contact members 26, Zl and 28 of relay ilCF are actuated to engage their respective front or first position contacts, and when the pilot circuit is open these contact members of relays ICE and 20F are actuated to engage their respective back or second position contacts. The manner of using this synchronous operation of the contact members of the code following relays 40F and 20F will appear as the specification progresses.

Two other line circuits extend between the stations DS and FS. One of these line circuits is a control and indication circuit which has a line wire 29 as one side of the circuit and is completed over the common return wire CL as the other side of the circuit. The other line circuit is an indication circuit which includes the line wire 30 extending between the two stations and is completed over the common return wire CL.

Referring now to the control and indication line circuit and looking at the field station FS, this control and indication circuit terminates in two parallel loop circuits and is associated with certain track switch and signal indication circuits. The remote control relays LGR and RGR are interposed one in each of the parallel loop circuits. Starting from the terminal M, at which the line wire 29 is terminaled at station FS, one loop circuit extends over front contact 18 of track relay 2TB, back contact 18 of relay WR, front contact 45 of relay RMR, winding iii of relay LGR, asymmetric unit 4?, and to the common return wire CL. The second loop circuit is the same up to back contact l9, and thence over front contact 48 of relay LMR, winding d9 of relay RGR, asymmetric unit 58 and the common return wire CL. The units ll and lit are disposed reverse to each other, the unit ll being disposed with its conducting or low resistance direction away from the common line wire, and the unit 58 being disposed with its conducting direction toward the common line wire. Consequently, when the potential of the terminal M is positive with respect to the common line wire, ciua'ent flows through the asymmetric unit 53 and the relay RGR is energized; when the potential of the terminal 44 is negative with respect to the common line wire, current flows through the asymmetric unit ll and the relay LGR is energized; and when the potential of the terminal M with respect to the common line wire is alternately positive and negative, then relays LG-R and RGR are both energized. The winding 46 of relay LGR is shunted by an asymmetric unit 5i, and the winding is of relay RGR is shunted by an asymmetric unit 52, so that these relays are slow releasing in character. The parts are so proportioned that when either relay LGR or RGR is energized by impulses of current of a frequency of 120 times per minute, that is, the operating frequency of the pilot line circuit, the relay remains picked up from one impulse until the next. The circuits at the field station associated with the control and indication line circuit for indicating the positions of the track switch and signals will. be taken up and explained when the operation of the apparatus is described.

At the office station, the control and indication line circuit terminates in two parallel loop circuits and is associated with certain control and indicating circuits. Starting from a terminal 81, at which the line wire 29 is terminaled at the office station DS, one loop circuit includes the respective back contacts 88 and 89 of relays RWE and NWE to be referred to later, wire 53, back contact 54 of a relay PER to be referred to later, asymmetric unit 55, winding 56 of an in dication relay RKP to be later described, and to the common return wire CL. The other loop circuit is the same up to back contact 54, thence over asymmetric unit 5?, winding 58 of an indication relay LKP to be referred to, and to the common return wire CL. The asymmetric units 55 and 5? are disposed reverse to each other, the unit 55 being disposed with its conducting direction toward the common wire CL, and the unit 51 being disposed with its conducting direction away from the common wire. Hence, when the potential of terminal 8? is positive with respect to the common wire, current flows through the unit 55 and the relay RKP is energized, and, when the potential of the terminal in is negative with respect to the common wire, current flows through the unit 51 and the relay LKP is energized. The relays LKP and RKP are each provided with slow release characteristics by virtue of an asymmetric unit 59 connected across the winding of relay RKP and an asymmetric unit $5 connected across the winding of relay LKP. The parts are so proportioned that, when the relays LKP and RKP are energized by current impulses of the code frequency rate of 120 times per minute, the relays remain picked up from one impulse until the next. The control and indicating circuits at the oiilce station associated with the control and indication line circuit will be referred to later.

Referring next to the apparatus at the ofiice station DS, a signal control lever LV and a switch control push botton PB are mounted for convenient manual operation. The lever LV is normally positioned at a mid position '11, as illustrated, and is operable to either a left-hand position Z or to a right-hand position 7. Five circuit controlling contact members 3|, 3d, 97, 98 and i0! are operatively connected with the lever LV for closing contacts at different positions of the lever. The push button P33 is of the spring return type and governs a relay PBR. In the normal position of the push button, the Winding 3? of relay PBR is short-circuited over the contact 38 of the push button and the relay is deenergized, but when the push button is depressed the short circuit is removed and a circuit is formed for energizing the relay. This circuit involves terminal B, back contacts 39, and ii of the relays LKP, RKP and OS, respectively, winding 32?, contact 42 of push button PB, resistance 43 and to the terminal C.

Three signal indication lamps ill, 62 and G3 are mounted preferably adjacent the signal lever LV to indicate the position of the signals at the track switch SW, the lamp iii being illuminated to indicate the stop position of the signals, the lamp 63 being illuminated to indicate a proceed position of either signal BA or RB, and the lamp 62 being illuminated to indicate a proceed position of either signal LA or LB. As will later appear, the lamp 6i also serves to indicate when the time element relay TE at the field station has operated. As here shown, these lamps are controlled by the two indication relays LR]? and RKP, the circuit for lamp 6i serially including back contacts G l and 65 of relays LKP and RKP, respectively; the circuit for lamp 62 including front contact 66 of relay RKP, lamp 62, controller contact ill-lit of lever'LV and a front contact ti of relay LKP; and the circuit for lamp @3 including front contact ill of relay LKP, lamp 63, controller contact i3iilll of lever LV, and front contact 68 of relay RICE.

To indicate the normal and reverse positions of the track switch SW, the oflice station apparatus is provided with a normal switch indication relay NWE and a lamp 6B, and a reverse switch indication relay RWE and a lamp iii. The relays NWE and RWE and their respective lamps E38 and iii are controlled in part by the indication relays LKP and EXP. At such time as the relay PBR is released and the indication relay RE]? is picked up, the relay NWE is. energized by virtue of a pick-up circuit extending from terminal B over back contact 85] of relay PER, front contact 85 of relay RKP, back contact 82 of relay RWE, winding 69 of relay NWE and to the terminal C. With relay NWE thus picked up, a stick circuit is formed over its front contact 33 which shunts around the front contact 85 of relay RKP, so that the relay NWE is retained energized subsequent to the release of the indication relay RKP. The lamp $8 is connected in multiple with the winding $9 of relay NWE and is thus illuminated whenever relay NWE is energized. At such time as the indication relay LKP is picked up and relay PER is released, a circuit is formed from terminal B over back contact 80 of relay PBR, front contact 83 of relay LKP, back contact 35 of relay NWE, winding H of relay RWE and terminal C, and the reverse switch indication relay RWE is energized. With relay RWE picked up, closing its front contact 86, a stick circuit is completed which shunts around the front contact 8 of relay LKP, so that relay RWE is retained energized subsequent to the rclease of the indication relay LKP. The lamp it is connected in multiple with the winding H of relay RWE and is illmninated whenever the relay is energized.

To provide the office station with an indication for the occupancy of the detector track section 2T. two relays LK and OS are included in the office station apparatus. The relay LK is controlled over a simple circuit including front contacts 90 and 9i of relays RKP and LKP, respectively. The control of relay OS will be pointed out when the operation of the apparatus is described.

A relay SS and related circuits may also be in cluded in the office station apparatus to provide an optional stick operation of the signals. The relay SS and its related circuits will be more fully described hereinafter.

Referring next to the indication line circuit and apparatus for indicating at the office station the occupancy of the track sections in the vicinity of the track switch, this line circuit terminates in two loop circuits at the ofdce station and which loop circuits extend between the line Wire 30 and the common return wire CL. One loop circuit comprises an asymmetric unit Hi l and the winding of a relay LAP, and the other loop circuit comprises an asymmetric unit W and the windof a relay RAP. The relay LAP controls at its front contact lllii a simple circuit for illuminating a lamp $1. of a track model TM, the circuit being supplied withcurrent from any convenient source the terminals of which are designated BX and CK. The relay RAP controls at its front contact Hit a simple circuit for illuminating the lamp IL of the track model. The asymmetric units H34 and WE are disposed reverse to each other, and thus the loop circuit including relay LAP is responsive to current of normal polarity and the loop circuit including relay RAP is responsive to currentofreverse polarity. The relays LAP and RAP are slow releasing in char acter by virtue of the asymmetric unitslilll and 2M being connected across the windings of the respective relays.

This indication line circuit is supplied with current at the field station FS over a circuit network controlled by the track relays and the code following relay ZCF. One path of this network includes terminal N of thebattery It, back contact iill of track relay lTR, and front contact ill of track relay 3TB. A. second path includes terminal B, front contact l l2 of relay ITR, and back contact llll of relay 3TB; and a third path in-- volves back contacts H3 and H ll and either back contact of contact member 28 of code following relay ZCF to terminal B of the current source, or front contact of contact member in to terminal N of the current source.

It follows that when the track section lT is occupied and section 3T is unoccupied current of nega ive or reverse polarity is supplied to this indication line circuit, and the relay RAP at the ()filCG. station is energized and lamp lL of the track model TM is illuminatedto indicate the occupancy of section lT. When section ST is occupied and section ii? is unoccupied, current of positive or normal polarity is supplied to the line circult and the relay LAP is energized and the lamp BL is illuminated to indicate the occupancy of section 3T. When both sections IT and 3T are occupied, then current alternately of normal and reverse polarity is supplied to the line circuit and both relays LAP and RAP are energized to illuminate both lamps 5L and BL of the track model.

In taking up the operation of the apparatus for controlling the switch and signals from the oifice station, I shall assume that at the start the switch SW is in its normal position, the signals are all at stop, the track sections are unoccupied and the apparatuses at the stations DB and FS are in the position illustrated, the lamp litl being illuminated to indicate the normal position of the switch, the lamp ill being illuminated to indicate the stop position of the signals, and the code transmitter EDC being active to operate the code following relays iCF and 2GB in synchronism. To operate the signal BA to a proceed position for an eastbound train, the operator moves the signal lever LV to its r position, closing contacts ill-33, it3t and til-Hill. During the next period the pilot line circuit is open and the code following relays lCF andflCF are released, a control current impulse of positive polarity is applied first to the indication relay RKP at the office station and then to the control relay RGR. at the field station over the control and indication line circuit. To be explicit, current first flows from terminal 13 of battery ll, over back contact of contact member .25 of relay lCF, contact 3l-33, front contact 92 of relay SS, front contact 93 of relay NWE, wire 53, back contact 5d of relay PER,

asymmetric unit 55, winding 56 of relay RKP and to the terminal. C of battery ll", and the relay RKP is picked up. Current then flows over the same circuit up to wire 53-, and thence over front contact 9&- of relay RKP, terminal ill, line wire 29 to the field station FS, terminal i l, front contact ill of relay 2TB, back contact is of relay WR, front contact til of relay LMR, winding 49 of relay RGR, asymmetric unit Ell and the common return wire CL to terminal (I of battery l7, and the relay is energized. When relay RGR is picked up, closing its front contact 73, the signal control relay RAH is energized as explained hereinbefore and the signal RA is operated to a proceed position. With the picking up of relay RAH, opening back contact interposed in the circuit for relay RMR, the relay RMR is deenergized and released.

During the next period that the pilot line circuit is closed and the code following relays are energized, an indication impulse of current of negative polarity flows from the C terminal of battery it at the field station over the common return wire CL to the office station, Winding 58 of indication relay LKP, asymmetric unit ill, back. contact 54, wire 53, front contact 9d, terminal 8i, line wire 29, terminal 44, front contact it, back contact "is, back contact 9 of relay RMR, front contact of the contact member 27 of relay 20F, and to the N terminal of battery H5, and the indication relay LKP is picked up. The picking up of relay LKP to close its front contact lil' completes the circuit for lamp 633, and lamp 53 is illuminated to indicate the proceed position of the signal RA. It is clear that a control impulse of current from battery ii is supplied to the relay RKP at the ofiice station and to the relay RGR at the field station during each period the pilot line circuit is open, an indication impulse of current from battery iii is supplied to the relay LKP during each closed period of the pilot line circuit, and these relays are retained energized from one impulse until the next by virtue of their slow release characteristics. Furthermore, these control impulses and indication impulses are alternately transmitted between the two stations over the same line circuit by virtue of the action of the code following relays.

Starting again with the apparatus in its normal condition, and assuming that the operator desires to operate the signal LA for a westbound train, the lever LV is moved to its Z position. During the next period that the pilot line circuit is closed and the code following relays are energized, a control impulse of current of negative polarity is supplied first to the relay LKP at the ofiice station and then to the control relay LGR at the field station. The circuit for relay LKP involves the following elements: terminal N of battery ll, front contact of contact member 24 of relay lCF, contact 3l-32, front contact 92, front contact 93, wire 53, back contact 54, asymmetric unit Lil, Winding 58 of relay LKP and terminal C of battery ll. The circuit for relay LGR involves the same elements up to wire 53, and thence over front contact 32 of relay LKP which is now picked up, terminal 87, line Wire 29, terminal 44, front contact 18, back contact l9, front contact 45 of relay RMR,winding 46 of relay LGR, asymmetric unit 41 and the common return wire to terminal C of battery [1. With control relay LGR picked up, closing its front contact 11, the signal control relay LAH is energized and the signal LA is operated to a proceed position in the manner explained hereinbefore. The relay LMR is deenergized and released when the signal control relay LAH is picked up, opening back contact 8. With relay LMR released, an indication impulse of current of posi tive polarity is returned to the office station during the next period the pilot line circuit is open and the code following relays are released. This impulse of current flows from terminal B of battery it over back contact of contact member 28 of relay ZCF, back contact I03 of relay LMR, back contact l9, front contact l8, terminal i4, line wire 29, terminal 8?, front contact E02 of relay LKP, wire 53, back contact 54, asymmetric unit 55, winding of relay RKP and the common return wire to the terminal C of battery [6, and the relay RKP at the office station is energized. With relay RKP picked up, closing its front contact 66, the circuit is completed for lamp 62, and that lamp is illuminated to indicate the proceed position of signal LA. From this point on, a control impulse of current of negative polarity from battery ll is supplied to the control and indication line circuit during each closed period of the pilot line circuit to energize the relays LKP and LGR, and an indication impulse of current of positive polarity from battery It is supplied over the control and indication line circuit during each open period of the pilot line circuit to energize the relay RKP, and these relays are retained picked up from one impulse until the next by virtue of their slow release characteristics.

Assuming the signal LA is operated in response to movement of the lever LV to its Z position and a westbound train enters the track section 3T to shunt the track relay 3TB, an indication impulse is supplied over the indication line circuit to the relay LAP by virtue of the closing of back contact H3 of track relay 3TB, and the lamp 3L of the track model TM is illuminated to indicate the presence of the train in section 3T. When the train advances into section 2T and shunts the track relay 2TB, the release of relay 2TB opens the control and indication line circuit at front contact ll; of relay 2TB, and the exchange of control and indication impulses between the two stations is stopped, and the relays LGR and RKP are deenergized and released. It is to be recalled that the relay LK at the office station is picked up when both relays LKP and BK]? are energized, so that when the relay RKP is now released the relay LK is in turn deenergized and releases at the end of its slow release period. During the interval the relay RKP is down and relay LK is picked up current flows from terminal B of battery I! through winding of relay OS, transfer contact H5 and back contact HG of relay OS, front contact I ll of relay LK, back contact H8 of relay RKP, controller contact 3435 of lever LV and terminal C, and relay OS is picked up. Relay OS is retained energized subsequent to the release of relay LK over a stick circuit which includes terminal B, winding of relay OS, transfer contact H5 and front contact H9 of relay OS, wire i255, terminal 81, line wire 29, terminal 44, back contact 12! of track relay 2TR, resistance i522 and common return wire to the terminal C of battery l1. With relay OS thus picked up, closing front contact I23, a simple circuit is completed for a lamp 2L of the track model TM to indicate occupancy of the track section 2T.

When the train enters the track section IT and shunts the track relay ITR, the relay RAP is energized in the manner explained hereinbefore, and the lamp lL is illuminated to indicate the presence of the train in section IT.

To require the operator to first restore the lever LV to its normal 11. position, in order to operate the signal LA for a second and following westbound train, the relay SS would be provided. The

relay SS is normally provided with current from terminal B over back contact E25 of relay OS, and contact member ml of lever LV in its normal position. Relay SS is retained energized subsequent to movement of the lever LV to its Z position by virtue of a stick circuit that includes two parallel paths, one path of which consists of back contact i235 of relay LK and the other path of which serially includes the front contacts l2? and I28 of relays RKP and LKP, respectively. Thus, during the interval between the release of relay RKP and the release of relay LK the relay SS is without current and is released, and relay SS upon releasing, opening its front contact 92, opens the circuit network at the oiiice station for the control and indication line circuit. To reclose the control and indication line circuit, the operator must restore lever LV to its normal position and pick up the SS relay, after which he can move the lever LV to its Z position to cause operation of the signal LA for a second westbound If the so-called stick operation of the signals is not desired, an emergency switch E29 would be closed and the relay SS constantly retained energized.

It is clear that the operation of indicating the occupancy of the track sections when the signal RA is operated for an eastbound train and an eastbound train moves through the sections lT, QT and 3T is substantially the same as that described above for a westbound train.

Again assuming that the apparatus is in its normal position and the operatorv desires to operate the track switch SW to its reverse position, the operator deprcsas the push button PB to pick up the relay PBR and then releases the push button so that relay PBR is released at the end of its slow release period. When the relay PBR is picked up, opening its back contact 83, the normal switch indication relay NWE is deener gized and the lamp 68 is extinguished. During the period that the pilot line circuit is open immediately following the release of relay NWE, a circuit is formed from terminal B of battery ll at the oiiice station over back contact of contact member 23 of relay iCF, normally closed contact $2 of push button PB, front contact Hill of relay PER, Wire 53, back contacts 82% and Fifi of relays NWE and RWE, terminal Bl, line wire 2%, terminal 4 front contact l3, back contact :8, front contact t3, winding -33 of relay RGR, asymmetric unit 5d, common return wire CL and to terminal C of battery H, and the relay RGR is picked up by this control impulse of current of positive polarity. During the next period the pilot line circuit closed. circuit is formed from the N terminal of battery I? at the office station, front contact of contact member 23 and over the same circuit traced above up to back contact 79 of relay WR at the field station, and thence over front contact winding 46 of relay LGR, asymmetric unit and the common return wire, and the relay LGR is picked up in response to this control impulse of current of nega tr e polarity. With both relays LGR and RGR energized, the switch controlling relay WR is operated in the manner explained hereinbefore for causing the switch mechanism SM to move the track switch to its reverse position. It should be here noted that the signal control relays are provided with slow-to-pick-up characteristics so that a signal control relay is not selected during the brief interval between the energizing of the first remote control relay and the energizing of the second remote control relay hy the switch control impulses. It should also be noted that loop circuits for the relays LGR and RGR are completed during the interval the switch is in mid position over front contact |I3i of relay WR and back contact it?! of relay KR.

iii

When. the switch is operated to its full reverse position and the relay KR is. energized in its reverse position, a reverse switch indication im pulse of current of reverse or negative polarity is supp-lied to the control and indication circuit for energizing the relay LKP at the office station, since the control impulses were stopped and relays LGR and RGR released when relay PBR released. The circuit involves terminal N of battery It at the field station, reverse polar contact iii? of relay KR, front contact Hil -l of relay KR, front contact MI of relay WR during the slow release period of relay WR, and the following elements: ill, it, 29, ill, 88, 39, I53, 54, ill, winding 58 of relay LE? and the common return wire. With relay LKP thus energized for the release period of relay WR, closing its front contact M, the reverse switch indication relay RWE is,

energized and the lamp It is illuminated to indi cate the reverse position of the switch.

To move the switch back to its normal position, the operator depresses the push button PB to pick up the relay PER. When relay PEI-iris thus picked up, opening its back contact llil, the relay RWE is deenergized and the lamp "ii! is extinguished. Immediately following the release of relay RWE, control current impulses alternately of positive and negative polarity are supplied to the control and indication circuit over the contact member of relay K33? and the front contact tilt of relay PER, and the control relays RGR and LGR at the field station are energized in the manner explained above. On the next step in the operation, the relay WR is supplied with current of normal polarity, since the circuit network IE3 is closed when the switch is moved to its reverse position and the network l i is open. With relay WR operated. to its normal position, the switch is moved back to its. normal position.

With relay KR energized by current of normal polarity in response to movement of the switch to the normal position, a normal switch indica tion impulse is supplied to the control and indication circuit, the circuit connection at the field station being the same previously described except that it now includes terminal B of the current source and the normal polar contact I35 of relay KB. This indication current impulse being of normal or positive polarity, the relay RKP at the ethos station is selected. With relay RKP selected and picked up, closing its front contact ill, the normal switch indication relay NWE is energized and the lamp E8 is illuminated.

Assuming that the signal lever LV has been operated to its 1" position, the signal control relay RAH picked up to operate the signal RA and the approach locking relay RMR released in the manner previously described, and that the operator then moves the lever LV back to its normal position n with a train approaching the signal RA so that thetrafiic controlled network 3 is open, the lamp 6! provides an indication of the completion of the selected time interval interposed by the relay TE in the reenergizing of the locking relay RMR. With relay RAH released, the repeater relay MP is energized, and with relay MP picked up, closing front contact EZI, the time element relay TE is operated to close its front contact 2H at the end of its selected operating period and the approach locking relay RMR is reenergized and then held energized over its front contact 222. During the op erating period of relay TE, the indication relay LKP is energized by virtue of the indication current impulses supplied over back contact 96 of relay RMR and the lamp 6| remains dark because its circuit is open at back contact G l of relay LKP. When locking relay RMR is picked up, the relay LKP is deenergized and releases, closing back contact 64 so that the lamp 5! is illuminated. Thus the illumination of the lamp llI, is an indication to the operator of the completion of the time interval interposed in the release of the approach locking.

A similar operation is efiected when the lever LV is restored to its 12 position after having been operated to its 1 position to govern the signal control relay LAH and a train has operated the traffic controlled network 6. This time, relay TE, upon operating to close its front contact 2H3, causes relay LMR to be reenergized. During the operating period of relay TE, the indication relay RKP is energizedby current impulses supplied over back contact I93 of relay LM'R and the lamp ill is dark because its circuit is open at back contact 65 of relay RKP. At the completion of the operation of relay TE, the reenergizing of relay LMR causes the lamp 6! to become illuminated and the operator is informed of the restoring of the approach locking relay.

It is to be seen, therefore, that the switch SW and its related signals are operated, and the occupancy oi the track section ET is indicated over the single control and indication line circuit extending between the two stations by virtue of the synchronous operation of the code following relays EC? and 20F, the difierent control conditions and the different indication conditions being effected through the medium of loop circuits selectively responsive to current of positive and negative polarity.

Referring now to Figs. 2a and 2b, the track layout is the same as in Fig. 1b except a track section 41 having a track circuit is formed in ie siding track. The apparatus at the field station F8 for operating the switch SW and its related signals is substantially the same as in Fig. 115 except two signal repeater relays RP and LP are provided to govern the control and indication line circuit in place of the approach locking relays RMR and LMR. The signal repeater relay RP is energized over a single circuit having two parallel paths, one of which includes a front contact I3? of relay RBH and the other path of which includes a front contact I36 of relay RAH. The relay LP is provided with an energizing circuit having two parallel paths, one path of which includes a front contact I38 of relay LAH and the other path of which includes a front contact I39 of relay LBH. It follows that relay RP is picked up whenever either signal BA or RE is operated to a proceed position, and the relay LP is picked up whenever either signal LA or LB is operated to a proceed position. I

The oifice station apparatus of Fig. 2a includes two slow releasing indication relays LKP and EXP, a signal control lever LV and signal indication lamps, a switch control push button PB and relay PBR, and. switch indication relays NWE and RWE with their respective lamps, the same as in Fig. la. The relays LK, OS and SS are omitted but the relay SS and related circuits may be added to the office station apparatus of Fig. 2a if desired.

The pilot circuit of Figs. 2a and 21) includes the line wires PL and CL and the two code following relays ICF and ZCF, the same as in Figs. 1a, and 1b, but the circuit difiers from that of Figs. 1a and 1b in that the code transmitter DC is located at the field station and is arranged to transmit at times an indication influence from the field station to the ofiice station during the normal open period of the pilot circuit. At the office station, an asymmetric unit I40 is interposed in the circuit adjacent the relay ICF and placed with its conducting direction toward the winding of relay ICF so that relay ICF is energized by current of positive polarity only. A relay OSI is associated with the pilot circuit at the oflice station by having one terminal or" its winding connected with the C battery terminal and the other terminal of its winding connected to the line wire PL through an asymmetric unit I42 and the back contact I43 of relay ICF, the unit I42 being disposed with its conducting direction toward the line Wire PL so that relay OS! is energized only when current of negative polarity is supplied to the pilot circuit. The relay OSI is made slow releasing by an asymmetric unit 2I6 being connected across its winding. At the field station, a connection is provided from terminal N of battery I 6 over back contact I44 of track relay 4TR, left-hand or second position contact of contact member I8 of the code transmitter DC and to line wire PL.

It follows that when the track section 4T is unoccupied the code transmitter DC periodically opens and closes the pilot circuit and the two code relays ICF and ZCF are operated in synchronism by the impulses of current of positive polarity supplied to the pilot circuit. When the section GT is occupied and track relay 4TB is released, the code following relays ICF and ZCF are operated the same as before, and during each half cycle that the contact member I 8 swings to the left-hand position an indication impulse of current of negative polarity is supplied to the pilot circuit and relay OSI is energized. Relay 08!, on picking up to close its front contact I45, completes a circuit for lamp 4L of the track model TMI, and lamp 4L is illuminated to indicate the occupancy of section 4T.

It should be pointed out that the code following relay 2CF may be omitted and the contact, members Hit, I5I and I613 of relay 2CF may be mounted on the code transmitter and operated in step with the contact member I8. In this latter case, the contact members I50 and I5I would be operated by the code transmitter DC to engage right-hand or first position contacts and to engage left-hand or second position contacts in step with the contact members I43, I 46 and M8 of relay ICF for governing the associated control and indication line circuit of Figs. 2a and 2b, and the contact member 260 would be operated by the code transmitter DC in step with the contact member I55 of relay ICF to govern the associated indication line circuit.

The control and indication circuit of Figs. 2a and 2b includes the line Wire 29 and the common return Wire CL, the same as in Figs. 1a and 112.

but the circuit diifers from the correspondingcircuit of Figs. 1a and 1b in that the circuit of Figs. 2a and 2b provides for control and indication of the track switch and related signals without the use of polarized loop circuits, without the use of asymmetric units to select the relays and without requiring what is commonly known as a split battery arrangement.

It is believed that the control and indication circuit of Figs. 2a and 2b can best be understood by a description of its operation. In describing the operation of the control and indication circuit of Figs. 2a and 21), I shall assume that the apparatus is in its normal position as illustrated in the drawings and the operator desires to operate the signal RA for an eastbound train. The signal lever LV is moved to its 1* position, closing contacts lib-33 and 98iflil. On the next open period of the pilot circuit, when the relays ICF and ZCF are deenergized, current is supplied first to the office relay RKP and then to the field station relay RGR. The circuit involved extends from terminal B of battery I'I over back contact of contact member I46 of relay ICF, lever contact 3! 33, back contact I41 of relay PBR, front contact 93 of relay NWE, a second back contact at of relay PER, back contact of contact member I48 of relay ICF, winding 56 of relay RKP and the terminal C of battery 11. With relay RKP picked up, the connection to the line wire 29 is completed at front contact 9 of relay REP and current flows over the line wire 29 to the field station and. thence through back conact 1- 3 of re'ay WR, back contact I49 of relay LP, winding 49 of relay RGR, back contact of contact member I50 of code relay ZCF and the common return wire CL to the C terminal of battery I'i. With relay RGR picked up, closing its front contact IS, the signal control relay RAH is selected and that relay on picking up operates the signal BA to a proceed position and at the same time energizes the relay RP. With the repeater relay RP picked up, closing its front contact I52, an indication impulse is supplied to the control and indication line circuit during the next period. the pilot line is closed. This indication circuit involves terminal B of the battery I6 at the field station, front contact of contact member I5! of relay ECF, front contact 452 of relay RP. back contact 79, line wire 29, front contact 96 of relay RKP, back contact 54, front contact of contact member I48 of relay ICF, winding 58 of relay LKP and the common return wire to the C terminal of battery I6. With re- ]ay LKP picked up, closing its front contact 61, the lamp circuit for lamp 63 is completed and lamp 553 is illuminated to indicate the proceed position of signal RA.

From this point on, the relay BKP at the office station and the relay RGR at the field station are each supplied with impulse of current from the battery I! during each period the pilot circuit is open, and the relay LKP at the offiice station is supplied with an impulse of current from the battery I6 during each period that the pilotv circuit is closed, these control and indication relays being retained energized from one impulse to the next by virtue of their slow release characteristics.

In case the lever LV is moved to its 1 position to close contacts 3I32 and ilk-99, the signal LA is operated to a proceed position and this position is indicated by the illumination of the lamp 62. This time, current flows from terminal B of battery I1 over front contact of contact member m6 of relay ICF, contact 3l-32, back contact l l'l, front contact 93, back contact 5t, front contact of contact member I48 of relay ICF, winding lid of relay LKP and to the terminal C, and the relay LKP on being energized completes the circuit to the line wire 29, and current then flows over the same circuit thus trace-d up to front contact 93 and thence over front contact Hi2 of relayLKP, line wire 29 to the field station, back contact 'lEl, back contact I54 of relay RP, winding Mi of relay LGR, front contact of contact member I50 of relay 26F, and the common return wire to theC terminal of battery ll. The picking up of relay LGR, closing its front contact .17, completes the circuit for the signal control relay LAH, and that relay is picked up to operate the signal LA and also to energize the relay LP.

An indication impulse is now supplied from battery it for energizing the relay RKP during the next period the pilot line circuit is open, the circuit extending from terminal B of battery It over back contact of contact member l5| of relay iiCF, frontcontact I53 of relay LP, back contact lil, line wire 29, frontcontact Hi2, back contact 54, back contact of contact mlember Mil of relay lCF, winding 56 of relay RKP and the common return wire to the C terminal of battery H5. With relay RKP picked up, closing its front contacttt, the circuit for lamp 62 is completed and the lamp is illuminated to indicate the proceed position of signal LA. From this point on, the relays LKP and LGR are supplied with a current impulse from battery ll during each period the pilot circuit is closed, and the relay RKP is supplied with an impulse of current from the battery It during each period the pilot circuit is open.

Assuming the apparatus of Figs. 2a and 2b to be at its normal position and that the switch SW is to be operated to its reverse position, the operator would depress the push button PB for an interval to energize the relay PER, in the manner previously explained. With relay PER picked up, the normal switch indication relay NWE and lamp (iii are deenergized, as previously explained. Current now fi'ows over the control and indication circuit to energize the relays LGR, and RGR, the circuit involving terminal 13 of battery ll, contact ii of push button PB, front contact lBil of relay PBR, back contacts fill and E8, line wire 29, back contact it, and thence over back contact 956 of relay RP and winding 46 of relay LGR to the common return wire when the contact member Hill engages its front contact, and over the back contact Hit of relay LP and the winding ii! of relay RGR to the common return wire when contact member ltd engages its back contact. With both control relays LGR and RGR energized, the switch controlling relay is supplied with current of reverse polarity, in the manner previously explained, to bring about the movement of the track switch to its reverse position. When the switch is moved to its full reverse position and relay KR is operated to its reverse position a reverse switch indication impulse is returned to the ofiice station, the circuit involving terminal B of battery 56, front contact of contact member lti of relay ZCF, reverse polar contact of relay KR, front contact 4%, front contact iii of relay WR, line wire 2t, back contacts and tit, back contact M, front contact of contact member Mil of relay ICF, winding of relay LKP, common return wire CL and to terminal C of battery It. With relayLKP picked up, closing its front contact 84, the reverse switch indication relay RWE and lamp iii are energized in the manner previously explained.

To move the track switch back to its normal position, the operator would depress the push button PB to pick up the relay PER for an interval. During the interval relay PBR is picked up, control current is supplied over the front contact ltil of relay PBR to the control and indication line circuit for energizing the relays LGR and RGR simultaneously, the two relays LGR and RGR being energized over the contact member 55%. This time, when the relays LGR and RG-R are both picked up, the switch controlling relay WR is energized with current of normal polarity, since the network ill is closed and the network 5 l is open, and the switch is operated back to its normal position. When the switch is moved to its full normal position and the relay KR is energized in its normal position, a normal switch indication impulse is returned to the ofiice station over the control and indication line circuit, the circuit being the same as described for the return of a reverse switch indication impulse, except at the field station it is completed at the back contact of contact member I 5! and includes the normal polar contact I35 of relay KR, and at the office station the circuit is completed to the relay RKP over the back contact of contact 'member M8 of relay ,ICF. With relay RKP thus energized, closing its front contact 6!, the normal switch indication relay NWE and lamp lid are energized to indicate the normal position of the switch.

It is to be seen, therefore, that, with the apparatus constructed as shown in Figs. 2a and 2?), control and indication impulses are exchanged between the two stations over a single line circuit by virtue of a synchronous operation of the code transmitter DC and the code following relays of the pilot circuit. The operation of the control and indication circuit of Figs. 2a and 2b differs from that of Figs. 1a and 1b in that the currents in the line circuit for control and indication flow in opposite directions in Figs. 2a and 21), whereas the currents flow in the same direction in Figs. la and lb. Also in Figs. 2c and 2b, the control relays LGR and RGR at the field station and the indication relays LKP and BK]? at the office station are selected by the definite time relation at which the relays are connected with the line circuit by the code transmitter and the code following relays in place of the polarity relation of the current supplied to the line circuit as used in Figs. la and lb.

In Figs. 2a and 2b, the indication circuit including line wire Bill for indicating the presence of a train in the track sections is governed by contact members of the code following relays of the pilot circuit in such a manner as to indicate occupancy of each of the track sections IT, 2T and any arrangement, and also to provide a special indication which may be used when indication of a track section is not required. At the office station this indication circuit is provided with four parallel loop circuits between the line wire til and the common return wire CL, two of which loop circuits are completed over a front or first position contact of contact member 1255 of code relay ICF and the other two of which loop circuits are completed over the back or second position contact of contact member I55. To be explicit, the first loop circuit includes an asymmetric unit I56 and the winding of a relay IS; the second loop circuit includes an asymmetric unit I5l and the winding of a relay 28; the third loop circuit includes an asymmetric unit I58 and the winding of a relay 3S; and the fourth circuit includes an asymmetric unit I59 and the winding of a relay 4S. The units I56 and I5? of the first and second loop circuits are disposed reverse to. each other, and the units I58 and I59 of the third and fourth loop circuits are disposed reverse to each other, and each of the four relays IS, 28, 3S and AS is made slow to release by virtue of an asymmetric unit connected across the winding of the relay, as will be understood by an inspection of Fig. 2a. It is clear that current of positive polarity supplied to the line wire 30 when the code relay ICE is energized selects the relay IS and current of negative polarity supplied to the line wire at such time selects the relay 23. In like fashion, current of positive polarity supplied to the line wire 30 when the code relay ICF is released selects relay 3S, and current of negative polarity selects the relay is.

The relays IS, 28, 3S and control a circuit network for illuminating the lamps IL, 2L and SL of the track model TMI, and a fourth lamp XL. Lamps IL, 2L and SL of the track model correspond to the sections IT, 2T and 3T, respectively, and the lamp XL corresponds to the condition of a special relay XR at the field station.

At the field station, the indication circuit is provided with impulses of current positive and negative in polarity in step with the operation of the contact member Hill of the code relay 20F in accordance with the arrangement of a circuit network which is controlled by the track relays ITR, 2TH and 3TB and the special relay KB. The track relays are responsive to traffic conditions on their respective track sections, and the relay XE would be used to check the condition of certain parts of the apparatus at the field station. For example, the relay XR could be used to check the voltage of the battery I5. This circuit network and the code member I are capable of establishing for each combination in which the track sections can be occupied a distinctive polarity pattern for the current impulses supplied to the indication circuit, and a different pattern for the release condition of the relay XR, with the result that the relays of the loop circuits at the ofilce station are selected in corresponding combinations and the lamps of the track model are illuminated in combinations corresponding to the combinations in Which the track sections are occupied, and the lamp XL is illuminated according to the condition of the XR relay.

In explaining the operation of the indication circuit of Figs. 2c and 2?), I shall first describe in step-by-step fashion the operation which takes place when an east-bound train travels through the track sections IT, ET and 3T. When the train enters track section IT and shunts track relay ITR, the indication circuit is supplied with current impulses which, starting from the instant the pilot circuit is closed and the code relays are energized, have a polarity pattern alt-ernately negative and positive. During the period the code relays are energized, the circuit extends from terminal N of battery It over back contact 553 of relay lTR, front contact Iii of relay 5TB, front contact of code contact member I of relay 26F, line wire 3!), front contact of contact member I55 of code relay ICF, asymmetric unit I51, winding of relay 2S and the common return wire to terminal C of battery I5, and relay its is energized. During the period the pilot circuit is open and the code relays are deenergized, the circuit extends from terminal B of battery I6 over front contact IGI of relay 2TB, back contact I82 of relay ITR, back contact of contact member I of relay ZCF, wire 35, back contact of contact member I55 of relay ICF, asymmetric unit it, winding of relay 3S and the common return wire to the terminal C of battery I5, and relay SS is energized. With both relays 2S and 3S picked up, the lamp IL is illuminated over a circuit having two branch paths, one path of which includes front contact I55 of relay 2S and the other path of which includes front contact Ifit of relay 3S and back contact I57. of relay IS.

When the train advances and enters section 2T and occupies both sections IT and 2T so that both track relays ITR and ZTR are shunted but track relay 3TB is picked up, the polarity pattern of the indication current is that of successive impulses of current of negative polarity. When the pilot circuit is closed, a first circuit is completed from terminal N of battery I6 over back contact I53 of relay iTR, front contact I66 of relay 3TR, front contact of contact member I50, wire 30, front contact of contact member I55, unit i5'I, winding of relay 2S and the common return wire to terminal C of battery It, and relay 2S is selected. A second circuit involves terminal N of battery It, back contact I68 of relay 2TB, front contact 565 of relay 3TH, back contact of contact member I59, wire BI), back contact of contact member I55, unit l59, winding of relay is and the common return wire to terminal C of battery I6, and relay E8 is selected. With relays 2S and is picked up, the lamp IL is illuminated over front contact I65 of relay 2S, and the lamp 2L is illuminated over front contact Ill! of relay 38.

Let us say that the train is long enough to cocupy all three sections IT, 2'1 and 3T so that all three track relays ITR, ETR and 3TB are shunted, the polarity pattern of the indication current is that of an impulse of current of negative polarity during the period the pilot circuit is closed and no impulse of current during the period the pilot circuit is open. When the pilot circuit is closed, a circuit now extends from terminal N of battery I6 over back contact Ill of relay 2TB, back contact N2 of relay ITR, back contact Il'3 of relay 3TH, front contact of contact member I60, wire 35, front contact of contact member I55, unit I 57, winding of relay 2S and the common Wire to terminal C of battery I5, and the relay BS is energized. During the period the pilot circuit is open, no circuit is completed and no impulse of current is supplied to the indication circuit. With relay is picked up, the lamp IL is illuminated over front contact I55 of relay 2S; the lamp 2L is illuminated over front contact I14 of relay 2S and back contact I'I5 of relay 3S; and the lamp 3L is illuminated over back contacts I16 and Ill of relays 65 and 38, respectively, and front contact I18 of relay 2S.

As the train advances, the section IT is vacated so that relay ITR is picked up and relays 2TB, and 3TH remain shunted. Under this combination of relays, the polarity pattern of the current supplied to the indication circuit is, starting with the pilot circuit closed, that of impulses of current alternately positive and negative in polarity. The first circuit consists of terminal n all contact member Hi0, wire 30, back contact of contact member H55, unit I59, winding of relay 4S and the common return wire to terminal C, and relay is is energized. With relays IS and selected, the lamp 2L is illuminated over front contact illiofrelay as, and the lamp 3L is illuminated over front contact IBI of relay is and front contact I82 of relay IS.

As the train. advances, the section 2T is next vacated and the relay 2TB is energized so that relays lTR and 2TB are now picked up and the relay .iTR is shunted. Under this combination of the relays, the indication current has a polarity pattern of successive impulses of current of positive polarity. The first circuit consists of battery terminal B, front contact no of relay ITR, back contact iii of relay 3TB, front contact of contact member I61], wire 33, front contact of contact member 555, unit .156, winding of relay ES, common return wire and terminal C, and relay I5 is energized. The other circuit extends from terminal 13 over front contact NH of relay 2TB, back contact 583 of relay 3TB, back contact of contact member, M39, wire 3i], back contact of contact member m5, unit I58, winding of relay common return wire and terminal C, and relay 38 is energized. The lamp 3L is now illuminated over front contact IB i of relay is and back contact Illtlof relay is. When the train moves east and vacates section 3T so that all three track relays are picked up, the indication circuit is without current and the lamps of thetrack model TMI are dark. I

In the event one train occupies section IT, a second train occupies section 3T and the section 2T is unoccupied, the relays lTR and 3TB. are shunted and relay 2TB. is. picked up. Under this combination of therelays, the polarity pattern of the indication current is that during the closed period of the pilot circuit no impulse of current is supplied to the indication circuit and during the open period of the pilot circuit an impulse of current of positive polarity is supplied to the indication circuit. This time, the circuit consists of terminal B, front contact ltI of relay 2TB, back contact I83 of relay 3TB, back contact of member I till, wire 3d, back contact of member Hi5, unit 458, winding of relay 3S, common return wire and terminal C, and relay BS is energized. The lamp H1. is now illuminated over front contact I66 of relay 3S and back contact l6! of relay is, and the lamp SL is illuminated over front contact I 84 of relay 3S and back contact Hit of relay 28.

Again asume the track section 2T is occupied and sections IT and 3T are unoccupied so that track relay 2TB is shunted and track relays lTR. and BTR are picked up. The polarity pattern of the indication current is now that no impulse is supplied during the closed period of the pilot circuit and current of negative polarity is supplied during the open period of the pilot circuit. The indication circuit now consists of terminal N, back contact I58 of relay 2TB, front contact Hit of relay 3TB, back contact of member Itll,

wire 30, back contact of member I55, unit I59,

to the wire 2GB.

Winding of relay 48, common return wire and terminal C, and relay is is selected. The lamp 2L is now illuminated over front contact Ill] of relay 4S.

When the track sections are unoccupied and relay XR is deenergized due to some condition of the apparatus, the indication circuit is supplied with an impulse of current of positive polarity during the closed period of. the pilot circuit and is without current during the period the pilot circuit is open. The circuit is completed from terminal B over back contact I38 of relay XR,

and thence as previously traced, and the relay IE5 is selected. With relay IS picked up, the lamp XL is illuminated'over front contact i871 of relay HS, back contact it? of relay is and back contact its of relay is.

It follows from the foregoing description of the indication circuit and apparatus of Figs. 2a and 211 that three continuing indications, which are independent of each other and ma therefore, be arranged in any combination, are transmitted over a single two-wire line circuit, and a fourth indication is transmitted when none of the other three indications are being used.

In Fig. 3, the tracklayout and signals are the same as in Fig. lb, except that an approach track section Al T having a track circuit is formed to the left of section IT. The signals and track switch of Fig. 3 are governed by apparatus at the field station which is controlled from the ofiice station over a control and indication circuit substantially the same as that of Figs. 2a and 2b,

and a description of this much of the apparatus need not be repeated, certain of the relays and circuits not being shown in Fig. 3 for the sake of simplicity.

In the form of the invention disclosed in Fig. 3, the pilot circuit extending between the two stations is operated by a code transmitter DCI at the ofiice station, and which transmitter is normally inactive and is approach controlled by trafiic conditions over the associated indication line circuit and by circuits governed by the signal lever LV and the switch controlling push button PB. At the field station a code repeater relay ECFP and another relay PR. are associated with the pilot circuit in a manner to be shortly described.

The code transmitter DCl may be of the same form as in Fig. 1a, but as shown in Fig. 3 it comprises two slow acting relaysT and TA.

At such time as positive energy is applied to the wire 2%, in a manner to later appear, current flows over back contact Zili of relay TA, Winding of relay T and to the terminal C of the current source, and relay T is picked up. Relay T, on picking up, closing front contact 262, completes a circuit and current flows from wire 2% over font contact 292, winding of relay TA and terminal C, and the relay TA is picked up. With relay TA picked up, the circuit for relay T is opened at back contact 26 i, and relay T releases at the end of its slow release period. Relay T, upon releasing to open front contact 23?, removes current from relay TA, and relay TA is released at the end of its slow release period. With both relays TA and T released and restored to their normal positions, the operating cycle explained above is repeated, and is periodically repeated as long as positive energy is applied The parts are so proportioned that the operating cycle of the code transmitter DCI requires one-half second, or, in other words, its code frequency is I20 cycles per minute, since I have assumed for illustrating my invention a code frequency of 12a cycles per minute for the pilot line circuit.

The pilot line circuit of Fig. 3 is controlled at back contact 2&3 of relay T, and consequently when the code transmitter DCl is active the code following relays ECF and 20F are operated sequentially, the same as described for the other forms of the invention. 1

The code repeater relay ZCFP is energized over two branch paths, one of which includes front contact of contact member I99 of code relay 20F, and the other path of which includes front contact I9i of relay PR. The repeater relay ZCFP is provided with slow pick-up and slow release characteristics, the parts being so adjusted that the pick-up period and the release period of relay ZCFP are each substantially equal to one-fourth of the operating cycle of the code following relays of the pilot circuit. Hence, when relay 2CFP is operated by virtue of the circuit completed at front contact of contact member 596 of relay EZCF, the two relays 2CF and ZCFP are operative to divide each code cycle into substantially four equal periods, which periods are about one-eighth second each in duration, when the code frequency of the pilot circuit is cycles per minute and each code cycle is of a duration of substantially one-half second. Starting from the instant the pilot circuit is closed, the relay ZCF is picked up and relay ZCFP is released during the first one-eighth second period of the cycle so that during this first oneeighth second period the front contacts of the contact members I65], M6 and I93 of relay ZCF and the back contacts of contact members 9% and I98 of relay ZCFP are closed; during the second one-eighth second period of the cycle the pilot circuit is still closed and both relays 2CF and ZCFP are picked up so that the front contacts of the contact members of both relays are closed; during the third one-eighth second period the pilot circuit is opened and relay 2CF immediately releases but relay ZCFP remains picked up due to its slow release feature so that the back contacts of the contact members of relay @CF and the front contacts of the contact members of relay 2CFP are closed during the third one-eighth second period; and during the fourth one-eighth second period the pilot circuit is still open and both relays ZCF and QCFP are released so that the back contacts of the contact members of both relays are closed. This operation of relays 20F and ZCFP is repeated for each successive code cycle. It should be noted, however, that the code relay ZCF of Fig. 3 operates sequentially with the relay ICF, the same as in the previous cases. The relay PR is introduced in the field station apparatus to at times effect approach control of the code transmitter TCI, in a manner to shortly appear.

In Fig. 3, the indication line circuit for indicating the occupancy of the track sections, and which circuit includes line wire 30, is provided at the office station with four parallel loop crcuits similar to Fig. 2a, and the description thereof need not be repeated except to point out that these loop circuits are controlled over the contact member I55 of code relay ICF.

The track model TM2 of Fig. 3 is similar to the track model TM of Fig. 1a except a lamp AIL has been added for indicating the occupancy of section AIT. The lamps of the track model TM2 are controlled by the office station indication relays over simple circuits which will be readily understood by an inspection of Fig. 3.

In describing the operations of the indication circuit of Fig. 3 for indicating the occupancy of the track sections and for approach controlling the code transmitter, I shall consider the operation effected in response to an eastbound train passing through the four successive track sections, the eastbound signal RA being operated after the train enters section AIT. It is noted that normally the code transmitter DC! is inactive, the code relays ICF and 20F are deenergized so that their respective contact members are in engagement with back or second position contacts, and the lamps of the track model TMZ are dark. When the train enters the approach section AIT and shunts the track relay AITR, the relay PR is energized by virtue of a circuit completed from terminal B of battery it, over back contact I92 of relay AITR,

back contact of contact member I93 of relay 26F, winding of relay PR and terminal C, and the relay PR is picked up at the end of its slow pickup period. Relay PR on picking up, closing its front contact I9 I causes current to be supplied to relay ZCFP, and relay 2CFP, on picking up, completes an indication circuit for energizing the relay 38 at the oihce station. This indication circuit can be traced from terminal B of battery It over back contact Hi2 of relay AlTR, front contact of contact member Hi l of relay ZCFP, back contact of contact member I50 of relay 20F, line wire 36, back contact of contact member G55 of relay ICF, asymmetric unit 558, winding of relay 3S and the common return wire to terminal C of battery 96. The relay 38 is ngw picked up, closing its front contacts I95 and I96, the closing of front contact I95 being effective to supply positive energy to wire 280 for operating the code transmitter DC! in the manner explained hereinbefore, and the closing of front contact E95 completing the circuit for lamp AIL for illuminating the lamp AEL to indicate the presence of the train in the section AIT. Operation of the code transmitter DC! and in turn of the code following relay 20F causes the relay PR to be deenergized and released, since the slow pick-up period of relay PR is made greater than the interval the back contact of contact member I93 of relay .ECF is closed. That is to say, the pickup period of relay PR is greater than one-half the code cycle of the pilot circuit. With relay PR released, the relay ZCFP is supplied with current over front contact of contact member Ifill of relay 2CF and is operated with the relay 20F to divide the code cycle into four periods, as already explained. The previously traced indication circuit for energizing relay SS in response to the train in section AIT is now formed during the third one-eighth second period of each code cycle, the connection being completed at back contact I92 of relay AlTR, front contact of contact member I96 of relay ZCFP and back contact of contact member of relay 20F, and thus the relay 38 at the office station is retained picked up, with the result the code transmitter DCI is continuously operated and the lamp AIL is continuously illuminated.

The track relay ITR is shunted when the head end of the train enters the section IT, so that both track relays ITR and AITR are now released. The indication relay continues to be supplied with current of positive polarity during the third one-eighth second period of each code .cycle, so that the lamp AIL is illuminated and the code transmitter is operated, the same as when the train. occupied the sectionAlT only. During the second one-eighth second period of each code cycle, an impulse of current of negative polarity is supplied to the indication circuit for energizing the relay 28, the connection at the field station being completed from battery terminal N over back contact lil-l of track relay l'IR, front contact of contact member [98, and front contact of contact member its of relay 20F, and the connection being completed at the office station over the front contact of contact member I55 of relay ICF, unit l"! and winding of relay 28. With relay is picked up, closing front contact tilt], the lamp IL is illuminated to indicate the occupancy of section IT. It should be noted that in case the train is short so that its rear end vacates the section AIT and the train occupies section IT only, the relay AITR picks up and deenergizes the indicationrelay 355 to discontinue the display of the lamp AIL, and the code transmitter DCl is controlled over front contact tilt of relay 2S.

Assuming the train is of such length that when its front end enters the section 2')? the train ex tends over sections AlT, VI and ET, the indication relays ES andkiS are retained energized by indication impulses supplied during the second and third one-eighth second period. of each code cycle, as explained alcove, so that the lamps AIL and lL are still illuminated. With the track relay shunted, impulses of current of positive polarity are supplied to the indication circuits during the first oneeighth second period of each code cycle to energize relay IS at the oflice station, the connection being completed at back contact tilt of relay 2TB, back contact of member Hill of elay RCFP and front contact of member Hill of relay 20F. The lamp 2L is now illuminated over front contact Mb of relay IS to indicate the occupancy of section 2T. It should be noted that with a short train which might occupy section 2T only, the operation of the code transnitter is maintained by the circuit includ his; front contact illll of relay is.

Assuming the train is of such length that when its head end enters section 3T the train occupies all four of the track sections, the relays i S, and are retained energ zed by i i n mp l supplied during the first, second and third oneeighth second period of each code cycle, and the lamps .AlL, l L and 21.. are still illuminated. The indicationrelay lS is now energized by impulses of current of negative polarity supplied during the fourth one-eighth second period of each code cycle, the connection being completed at back contact tilt of relay back contact of member Hi l of relay QCFP and back contact of member Hill of relay lZCF. The closing of front contact of relay ts completes the circuit for lamp 3L, and lamp FL is illuminated to indicate the presence of the train insection ET, and the closing of front contact tilt of relay M3 completes another parallel path for supplying energy to the code transmitter DCI.

Starting again with the apparatus in its normal condition and asu ning a westbound train. enters the section ET and shunts track relay 3TH, the indication relay is is picked up by virtue of cur-- rent supplied from terminal N over back contact llill ofrelay and back contacts of members ldtl, lllll and ltiii of relays ZCFP, ZZCF and lCF, respectively With relay lS picked up, closing its front contacts iltllland 209, the lamp 3L is illuminated and positive energy is supplied to the code transmitter DC! to start operation of the transmitter. The operations effected from. this point on in response to the westbound train occupying the sections 2T, IT and AIT are similar to the operations effected in response to the eastbound train occupying these sections, and it is thought the description need not be repeated.

Starting again with the apparatus in the normal condition and assuming a signal. is to be operated while the track sections are unoccupied, the operator moves the signal lever LV of Fig, 3 to either its Z or 1" position to control the relays LGR and RGR, in the manner explained in Figs. 2a and 222. When the signal lever LV is moved to either position I or 1', positive energy is supplied to wire lllll over the contact member ill of lever LV', and the code transmitter DCl is operated to operate the code following relays so that the signal control for operating the signals and the indication of the positions of the signal is effected over the control and indication line circuit in the same manner as described for Figs. 2c and 2b.

Again, if the operator desires to move the track switch, and to that end depresses the push button PB to pick up the relay PBR, positive energy is applied to wire Eiltl over a connection including back contacts Eli and 2l3 of the switch indication relays NWE and RWE so that the code transmitter DCl is set into operation and the relays LGR and RGR are made responsive to the switch controlling impulse and the position of the switch is indicated over the control and indication line circuit in the same manner as described for Figs. 2a and 2b.

It is apparent that with the apparatus of Fig. 3, the code transmitter is made active only when a signal or the track switch is to be operated and the occupancy of a track section is to be indicated, and that the indications of the occupancy of four track sections are transmitted over a single two-wlre line circuit Although I have herein shown and described. only three forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended. claims without departing from the spirit andscope of my invention.

Having thus described my invention, what I claim is:

l. In a remote control system, an ofiice station and a field station, a pilot circuit connecting said stations and including in series the windings of two code following relays one at each station,

a code transmitter operative to periodically open 2. In a remote control system, an office station and a field station, a pilot circuit connecting said stations and serially including the windings of two code following relaya said relays located one at each of said. stations, a code transmitter operative to code said circuit to operate said relays in synchronism, and control and indication circuit extending between said stations jointly controlled bysaid relays and made effective to alter nately exchange current impulses between said stations according to the code operation of said transmitter by such synchronous operation of said relays.

' cation means, a control lever at the ofiice sta- 3. In a remote control system, an ofiice station and a field station, a pilot circuit extending between said station and serially including the windings of two code following relays, said relays located one at each of said stations, a code transmitter operative to periodically open and close said circuit to operate said relays in synchronism, a line circuit extending between said stations, control apparatus at the field station having a plurality of difierent conditions, controlling means at the ofiice station having a position for each condition of the control apparatus, and means governed by said relays to selectively connect said controlling means and control apparatus to said line circuit to establish the condition or the control apparatus corresponding to the position of the controlling means.

4. In a remote control system, an ofiice station and a field station, a control device at the field station, an indication device at the office station, a pilot circuit extending between said stations and including series the windings of two code following relays one at each station, a code transmitter operative to periodically open and close said circuit for operating said relays in synchronisrn, a line circuit extending between said stations, a current source, means governed by said relays to connect the current source with said line circuit first at the office station and then at the field station and to periodically alternate the connections, and other means governed by said relays to alternately connect the control and ind.:' cation. devices with said line circuit to energize the devices each with current supplied to said 1 line circuit at the other station.

5. In a remote control system, a mechanism having different positions, a field station at said mechanism having a control means selectively responsive to current of normal and reverse polarities for operating said mechani m, an office station having an indication means selectively responsive to current of normal and reverse polarities for indicating the positions of said mecha pilot circuit extending between said stations and including in series the windings of two code following relays one at each station, a code transmitter operative to periodically open and close said circuit to operate said relays in synchronism, another circuit extending between said stations and connected to said control and inditions, means controlled by said lever and the station code relay to supply current impulses of either normal or reverse polarity to said other circuit during the opened or closed periods of the pilot circuit respectively to selectively energize said control means for operating the mechanism, and means controlled by said mechanism and the field station code relay to supply current impulses of either normal or reverse polarity to said other circuit during the opened or closed periods of the pilot circuit respectively to selectively energize said indication means, and said code following relays arranged that current can be supplied to said other circuit at but one station at a time.

6. In a remote control system, an office station and a field station, a pilot circuit extending between said stations and including two relays one at each station, said relays each operable to a first position when energized and to a second position when deenergized, coding means operative to periodically open and close said circuit to operate the relays in synchronism, a control circuit extending between said stations, two loop circuits at each station connected with said control circuit, said loop circuits each including a control unit and each operative to pass current in one direction only and the two loop circuits at each station arranged for opposite directions, a control lever at the oifice station having a first and a second position, means including the first position of the lever and the first position of the ofiice relay to supply current of reverse polarity to said control circuit to energize the unit of a particular one of the field station loop circuits, means including the second position of the lever and the second position of the office relay to supply current of normal polarity to said control circuit to energize the unit of the other field station loop circuit, means controlled by the unit of said one field station loop circuit and the second position of the field station relay to supply current of normal polarity to the control circuit to energize the unit of a particular one of the ofiice station loop circuits and means controlled by the unit of said other field station loop circuit and the first position of the field station relay to supply current of reverse polarity to the control circuit to energize the unit of the other office station loop circuit.

7. In a remote control system, a railway track provided with a signal for governing traffic over said track, a field station located at said signal and having a control device for governing said signal, an ofi'ice station remote from the signal and having an indication device for indicating the position of said signal, a pilot circuit extending between said stations and including two code following relays one at each station, a code transmitter operative to periodically open and close said circuit for operating said relays in synchronism, another circuit extending between said stations, a current source, means controlled by said relays to periodically and alternately connect said control and indication devices to said other circuit, and other means governed in part by said relays to periodically connect the current source to said other circuit alternately at the two stations to energize said control and indication devices each by current supplied to said other circuit at the opposite station whereby the signal is continuously controlled from the ofiice station and the indication device is continuously controlled from the field station.

8. In a remote control system, a stretch of rail- Way track, a right signalling means and a left signalling means to govern traffic through the stretch, a field station adjacent said stretch, a remote office station, a pilot circuit extending between said stations including two code following relays one at each station, said code relays each operable to a first and a second position, coding means to periodically open and close said circuit to operate said relays to their first and second positions in synchronism, another circuit extending between said stations, a first and a second loop circuit at each station connected to said other circuit, each of said loop circuits including a control unit and operative to pass current of one polarity only and the two circuits at each station arranged for opposite polarities, a signal lever at the office station having a right and a left position, means including the right position of the lever and the second position of the office relay to supply current of normal polarity to said other circuit to energize the unit of the first field loop circuit, means including the left position of the lever and the first position of the office relay to supply current of reverse polarity to said other circuit to energize the unit of the second field loop circuit, circuits governed by the control units of the field loop circuits for selectively operating said right and left signalling means, means governed by said right signalling means and the first position of the field relay to supply current of reverse polarity to said other circuit to energize the unit of the first oifice loop circuit, means governed by said left signalling means and the second position of the field relay to supply current of normal polarity to said other circuit to energize the unit of the second omce loop circuit, and indicating devices selectively governed by the control units of the ofiice loop circuits.

9. In a remote control system, an office station and a field station, a pilot circuit extending between said stations and including in series the windings of twocode following relays one at each station, said relays each operable to a first and a second position, coding means having an operation cycle of a predetermined periodand operative to periodically open and close said pilot circuit for substantially one-hali of each cycle respectively to operate said relays to their first and second positions in synchronism, a slow release control relay at the field station and a slow release indication relay at the office station, said slow release relays having slow release periods greater than onehalf the period of said operation cycle, a line circuit extending between said stations, a current source at each station, means includingthe first position of each of said code relays to connect said control relay at the field station and the current source at the office with the line circuit to continuously energize the control relay due to its slow release period bridging the second position periods of the code relays, and means including the second position of each of said code relays to connect said indication relay at the oifice station and the current source at the field station to the line circuit to continuously energize the indication relay due to its slow release period bridging the first position periods of the code relays.

10. In a remote control system, an office station and a field station, a pilot circuit extending between said stations and serially including the windings of two code following relays one at each station, said relays each operable to a first and a second position, coding means having an operation cycle of a predetermined period and operative to periodically open andclose said circuit to operate said relays to their first and second positions in synchronism with each relay at its respective positions for substantially one-half of each cycle, a control unit and a signalling means at the field station, an indication unit and a lamp at the ofiice station, said control and indication units provided each with a slow acting period greater than one-half the period of said operation cycle, a control lever, a line circuit extending between said stations, a current source at each station, means governed by said lever and including the first position of each of said code relays'to connect the control unit at the field and the current source at the ofiice with said line circuit to continuously energize the control unit for governing said signalling means, and means governed by the signalling means and including the second position of each of said code relays to connect the indication unit at the office and the current source at the field to said. line circuit to continuously energize the indication unit for illuminating the lamp.

11. In a remote control system, an ofiioe station and a field station, a pilot circuit extending between said stations and serially including the windings of two code following relays one at each station, said relays each operable to a first and a second position, coding means having an operation cycle of a predetermined period and operative to periodically open and close said circuit to operate said relays to their first and second posi tions in synchronism with each relay at its respective positions for substantially one-half of each cycle, a first and a second slow release control relay and a signalling means at the field station, a first and a second slow release indication relay and a pair of lamps at the ofilce station, said control relays and said indication relays provided each with a slow release period greater than one-half of said operation cycle, a control lever having a first and a second position, a line circuit extending between said stations, a current source at each station, means including the first position of the lever and the first position of both code relays to connect the current source at the office and the first control relay with said line circuit for continuously energizing that relay because of its slow release period to establish a first condition of said signalling means, means including the second position of the lever and the second position of both code relays to connect the current source at the omce and said second control relay with said line circuit for continuously energizing that relay because of its slow release period to establish a second condition of the signalling means, means including the first condition of the signalling means and the second position of both code relays to connect the current source at the field and said first indication relay with said line circuit for continuously energizing that relay because of its slow release period to illuminate a first one of said lamps, and means including the second condition of the signalling means and the first position of both code relays to connect the current source at the field and said second. indication relay with said line circuit for continuously energizing that relay because of its slow release period to illuminate the second one of said lamps.

12. In a remote control system, an ofiice station and a field station, a pilot circuit extending between said stations and serially including the windings of two code following relays one at each station, said relays each operable to a first and a secondposition, coding means having an operation cycle of a predetermined period and operative to periodically open and close said circuit to operate said relays to their first and second positions in synchronism with each relay at its respective positions for substantially one-half of each cycle, a slow release control relay and. a signalling means at the field station, a slow release indication relay and an indicator as well as a control lever at the office station, said control and indication relays provided each with a slow release period greater than one-half the period of said operation cycle, a line circuit extending be tween said stations, a current source at each station, means governed by said lever and including the first position of both code relays to connect said control relay and the current source at the omce with said line circuit for continuously energizing said control relay because its slow release period bridges the second position periods of the code relays to maintain a given 

